Changes in dietary fiber fractions and gut microbial fermentation properties of wheat bran after extrusion and bread making

Jennifer A Arcila; Steven A Weier; Devin J Rose

doi:10.1016/j.foodres.2015.05.005

Changes in dietary fiber fractions and gut microbial fermentation properties of wheat bran after extrusion and bread making

Food Res Int. 2015 Aug:74:217-223. doi: 10.1016/j.foodres.2015.05.005. Epub 2015 May 8.

Authors

Jennifer A Arcila¹, Steven A Weier², Devin J Rose³

Affiliations

¹ Department of Food Science & Technology, University of Nebraska-Lincoln, Lincoln, NE, USA.
² The Food Processing Center, University of Nebraska-Lincoln, Lincoln, NE, USA.
³ Department of Food Science & Technology, University of Nebraska-Lincoln, Lincoln, NE, USA; Department of Agronomy & Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA. Electronic address: drose3@unl.edu.

PMID: 28411986
DOI: 10.1016/j.foodres.2015.05.005

Abstract

The dietary fiber in wheat bran, principally non-starch polysaccharides (NSP), is mostly water-unextractable and is poorly utilized by human gut microbiota. The purpose of this study was to determine the change in water-extractability of NSP in wheat bran upon extrusion and then to determine if extrusion impacts the availability of NSP for fermentation by the fecal microbiota during in vitro fecal fermentation. A secondary objective was to incorporate extruded bran into a product formulation to determine if changes in WE-NSP and NSP fermentation were maintained in a finished product. Bran was extruded using combinations of high or low moisture (15% and 30% wb) and high or low screw speed (120 and 250rpm). All extrusion conditions resulted in increases in WE-NSP and fecal microbiota short chain fatty acid (SCFA) production upon fermentation compared with unextruded bran. Low screw speed and low moisture resulted in the greatest increase in WE-NSP (3-fold) as well as the highest production of SCFA during fermentation (1.4-fold) compared with unextruded bran. Whole wheat breads containing extruded bran did not show increases in either WE-NSP or SCFA production compared with the control. In conclusion, extrusion of wheat bran increased WE-NSP, which enabled greater fermentability by human fecal microbiota. However, once extruded bran was used in a whole wheat bread formulation the changes in fermentation outcomes were no longer evident.

Keywords: Arabinoxylans; Butyrate; Moisture; Non-starch polysaccharides; Screw speed; Short chain fatty acids.